Add equals_na_linter (#326)

Closes #143

DESCRIPTION

@@ -47,6 +47,7 @@ Collate:
     'comments.R'
     'object_name_linters.R'
     'deprecated.R'
+    'equals_na_lintr.R'
     'exclude.R'
     'expect_lint.R'
     'extract.R'

NAMESPACE

@@ -24,6 +24,7 @@ export(default_linters)
 export(default_settings)
 export(default_undesirable_functions)
 export(default_undesirable_operators)
+export(equals_na_linter)
 export(expect_lint)
 export(expect_lint_free)
 export(extraction_operator_linter)

NEWS.md

@@ -54,6 +54,7 @@
 * Changed `lint_package` to remove fully excluded files as soon as possible to
   avoid reading and pre-processing of ignored files (@mwaldstein)
 * Allow for any number of `#` to start a comment. Useful in ESS (#299, @prosoitos)
+* New equals_na_linter() (#143, #326, @jabranham)
 
 # lintr 1.0.2 #
 * Fix tests to work with upcoming testthat release.

R/equals_na_lintr.R

@@ -0,0 +1,38 @@
+#' @describeIn linters that checks for x == NA
+#' @export
+equals_na_linter <- function(source_file) {
+  all_matches <- re_matches(
+    source_file$lines,
+    rex("==", zero_or_more(" "), "NA"),
+    locations = TRUE,
+    global = TRUE
+  )
+  line_numbers <- as.integer(names(source_file$lines))
+
+  Map(
+    function(line_matches, line_number) {
+      lapply(
+        split(line_matches, seq_len(nrow(line_matches))),
+        function(match) {
+          start <- match[["start"]]
+          if (is.na(start)) {
+            return()
+          }
+          end <- match[["end"]]
+          Lint(
+            filename = source_file$filename,
+            line_number = line_number,
+            column_number = start,
+            type = "warning",
+            message = "Use is.na rather than == NA.",
+            line = source_file$lines[[as.character(line_number)]],
+            ranges = list(c(start, end)),
+            linter = "equals_na_linter"
+          )
+        }
+      )
+    },
+    all_matches,
+    line_numbers
+  )
+}

R/zzz.R

@@ -89,6 +89,7 @@ default_linters <- with_defaults(default = list(),
   closed_curly_linter(),
   commas_linter,
   commented_code_linter,
+  equals_na_linter,
   function_left_parentheses_linter,
   infix_spaces_linter,
   line_length_linter(80),

tests/testthat/test-equals_na_linter.R

@@ -0,0 +1,21 @@
+context("equals_na_linter")
+
+test_that("returns the correct linting", {
+  msg <- rex("Use is.na rather than == NA.")
+  expect_lint("blah", NULL, equals_na_linter)
+  expect_lint("  blah", NULL, equals_na_linter)
+  expect_lint("  blah", NULL, equals_na_linter)
+  expect_lint("x=NA", NULL, equals_na_linter)
+
+  expect_lint(
+    "x == NA",
+    list(message = msg, line_number = 1L, column_number = 3),
+    equals_na_linter)
+
+  expect_lint(
+    "x==NA",
+    list(message = msg, line_number = 1L, column_number = 2),
+    equals_na_linter
+  )
+
+})